1. Field of the Invention
The invention generally relates to an automatic method for a scanner, and more particularly relates to a method for determining the position of a document placed in the scanning widow of a flatbed scanner.
2. Related Art
Automatic methods for a flatbed scanner to determine the position of a document placed on the scanner window are already well known. However, the prior methods are limited to the application of flatbed scanners that have a single background pattern of the scanner window. In other words, the prior method obtains a background image pattern of the scanner window by a pre-scanning process, then the background image pattern (a certain image color) can be omitted later from automatic ranged scanning so as to produce the document image only. When the prior method is applied to a flatbed scanner with two kinds (two colors) of background image pattern, incorrect determining of the document range may occur.
For example, beside a common black or white pressing cover for the flatbed, a conventional scanner may include an illuminator for lighting a transparency or a film for scanning. The illuminator has a color different from that of the pressing cover. Therefore, with the prior method the scanner mistakes the image of the illuminator as a part of the scanned document if only one background color (the color of the pressing cover) is considered. Or, a partial image of the scanned document is cropped if two background colors are considered.